[root@cwdtest1 ~]# strace -f -F -ff -o mysqld-strace -s 1024 -p 62509 strace: Process 62509 attached with 32 threads .... strace: Process 33059 attached
[root@cwdtest1 /]# mysql -uroot -pcwdroot mysql: [Warning] Using a password on the command line interface can be insecure. Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 24 Server version: 5.7.23-23-log Source distribution Copyright (c) 2009-2018 Percona LLC and/or its affiliates Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select * from cwdtest.test; +---------+----------+ | col1 | col2 | +---------+----------+ | | aaaaaaaa | | ccccccc | NULL | +---------+----------+ 2 rows in set (0.00 sec) mysql> exit Bye
从performance_schema.threads中可以看到新增的54号前台线程thread/sql/one_connection，其os 线程id是33059
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*************************** 31. row *************************** THREAD_ID: 54 NAME: thread/sql/one_connection TYPE: FOREGROUND PROCESSLIST_ID: 28 PROCESSLIST_USER: root PROCESSLIST_HOST: localhost PROCESSLIST_DB: NULL PROCESSLIST_COMMAND: Sleep PROCESSLIST_TIME: 10 PROCESSLIST_STATE: NULL PROCESSLIST_INFO: NULL PARENT_THREAD_ID: 1 ROLE: NULL INSTRUMENTED: YES HISTORY: YES CONNECTION_TYPE: Socket THREAD_OS_ID: 33059 《====== 31 rows in set (0.00 sec)
set_robust_list(0x7f9aa60ea9e0, 24) = 0
gettid() = 33059
setsockopt(67, SOL_TCP, TCP_NODELAY, [1], 4) = -1 EOPNOTSUPP (Operation not supported)
setsockopt(67, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
open("/dev/urandom", O_RDONLY) = 68
read(68, "'\275|\274\277\200Uw\2205\3)M\4E\364C\372\210\222\235\345\33I\216\252\206M\336C;\372", 32) = 32
close(68) = 0
之后是密码验证，以及一些版本消息等
sendto(67, "Q\0\0\0\n5.7.23-23-log\0\34\0\0\0{PR&1|0 \0\377\367!\2\0\377\201\25\0\0\0\0\0\0\0\0\0\0\4\26:5.h\34U\"G%a\0mysql_native_password\0", 85, MSG_DONTWAIT, NULL, 0) = 85
recvfrom(67, "\272\0\0\1", 4, MSG_DONTWAIT, NULL, NULL) = 4
recvfrom(67, "\205\246\377\1\0\0\0\1!\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0root\0\24\v\10A\216\"\344i\31'\331UMa\"\356\4\3640!\331mysql_native_password\0i\3_os\5Linux\f_client_name\10libmysql\4_pid\00533058\17_client_version\t5.7.23-23\t_platform\6x86_64\fprogram_name\5mysql", 186, MSG_DONTWAIT, NULL, NULL) = 186
sendto(67, "\7\0\0\2\0\0\0\2\0\0\0", 11, MSG_DONTWAIT, NULL, 0) = 11
recvfrom(67, "!\0\0\0", 4, MSG_DONTWAIT, NULL, NULL) = 4
recvfrom(67, "\3select @@version_comment limit 1", 33, MSG_DONTWAIT, NULL, NULL) = 33
sendto(67, "\1\0\0\1\1'\0\0\2\3def\0\0\0\21@@version_comment\0\f!\0009\0\0\0\375\0\0\37\0\0\24\0\0\3\23Source distribution\7\0\0\4\376\0\0\2\0\0\0", 83, MSG_DONTWAIT, NULL, 0) = 83
recvfrom(67, 0x7f9a9000a730, 4, MSG_DONTWAIT, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=67, events=POLLIN|POLLPRI}], 1, 28800000) = 1 ([{fd=67, revents=POLLIN}])
接受到shelect 的查询语句，我们可以看到 会stat ./cwdtest/test.frm 这个文件，这里是 获取文件信息，并在去访问./cwdtest/test.TRG，发现提示No such file or directory。
recvfrom(67, "\33\0\0\0", 4, MSG_DONTWAIT, NULL, NULL) = 4
recvfrom(67, "\3select * from cwdtest.test", 27, MSG_DONTWAIT, NULL, NULL) = 27
stat("./cwdtest/test.frm", {st_mode=S_IFREG|0640, st_size=8590, ...}) = 0
access("./cwdtest/test.TRG", F_OK) = -1 ENOENT (No such file or directory)
sendto(67, "\1\0\0\1\2-\0\0\2\3def\7cwdtest\4test\4test\4col1\4col1\f!\0\36\0\0\0\375\1\20\0\0\0-\0\0\3\3def\7cwdtest\4test\4test\4col2\4col2\f!\0\36\0\0\0\375\0\0\0\0\0\n\0\0\4\0\10aaaaaaaa\t\0\0\5\7ccccccc\373\7\0\0\6\376\0\0\"\0\0\0", 141, MSG_DONTWAIT, NULL, 0) = 141
recvfrom(67, 0x7f9a9000a730, 4, MSG_DONTWAIT, NULL, NULL) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=67, events=POLLIN|POLLPRI}], 1, 28800000) = 1 ([{fd=67, revents=POLLIN|POLLHUP}])
recvfrom(67, "\1\0\0\0", 4, MSG_DONTWAIT, NULL, NULL) = 4
recvfrom(67, "\1", 1, MSG_DONTWAIT, NULL, NULL) = 1
shutdown(67, SHUT_RDWR) = 0
close(67) = 0
futex(0x1dca184, FUTEX_WAIT_PRIVATE, 46, NULL
(END)
[root@cwdtest1 cwdtest]# hexdump -C -v test.frm
00002130 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | | 00002140 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 00 | .| 00002150 04 00 05 63 6f 6c 31 00 05 00 05 63 6f 6c 32 00 |...col1....col2.| 00002160 04 05 1e 1e 00 02 00 00 00 40 00 00 00 0f 21 00 |.........@....!.| 00002170 00 05 05 1e 1e 00 21 00 00 00 80 00 00 00 0f 21 |......!........!| 00002180 00 00 ff 63 6f 6c 31 ff 63 6f 6c 32 ff 00 |...col1.col2..|
40表示不可为空，(DEFAULT NULL 80,NOT NULL 40,DEFAULT 'VALUE' 00)
0f表示字段类型是varhcar 21表示字符集是utf8
表创建语句：
| test | CREATE TABLE `test` ( `col1` varchar(10) NOT NULL, `col2` varchar(10) DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
